The invention relates to an apparatus for evening the sliver or lap in a carding machine, a roller card unit or similar apparatus which has a licker-in (fiber opening roller), a feed roller arranged upstream of the licker-in as viewed in the direction of material feed and a feed table cooperating with the feed roller. Generally, the feed table is biased towards the stationarily supported feed roller and is arranged for shifting motion towards and away from the feed roller as a function of the thickness (quantity) of the fiber material passing through the clearance defined between the feed table and the feed roller. The feed table is associated with a measuring member for generating a signal representing the amount of excursion of the feed table.
In a known apparatus disclosed in French published application No. 2,322,942, underneath the stationary feed roller there is arranged a stationary support on which a plurality of sensor levers (feed table) are movably held. One end of the sensor levers is in the immediate vicinity of the licker-in and is spring loaded. The other end of each sensor lever is joined by a measuring device (sensor pedals) which responds to the shifts of the sensor lever as the latter moves as a function of the thickness of the fiber material passing through. The measuring location is the region between the feed roller and the feed table where the deviation of the thickness of the material is determined. In the prior art apparatus the measuring location is situated in the clamping zone between the feed roller and the sensor levers since the feed roller is immediately opposite the sensor levers. The measuring zone begins already at a location where the fiber material enters into the clamping gap. The working location is the zone where the fiber material is taken over by the licker-in. At that location, by virtue of an acceleration or deceleration of the rpm of the feed roller, lesser or greater quantities of fiber material are taken over by the licker-in and thus a correction (regulation) of the thickness deviation takes place. The time and path difference between measuring location and working location is a disadvantage because when at the measuring location a thickness deviation is sensed and by virtue of the control device the rpm of the feed roller is immediately altered, at the same moment at the working location (where the correction is supposed to take place) a correction of the material thickness is effected at a zone other than the intended region. When, conversely, the location of the fiber material to be corrected reaches the working zone, the feed roller, based on the further rpm changes that occur in the meantime, may have an rpm which cannot bring about the desired correction of the thickness deviation.
According to another known apparatus disclosed in U.S. Pat. No. 4,275,483, the feed roller is biased and is movably supported for a shifting motion relative to a stationary feed table as a function of the thickness of the introduced fiber material. The disadvantages relative to the measuring zone and the discrepancy between the measuring location and the working location which were discussed in connection with the prior art represented by French published application 2,322,942 are equally present in the prior art disclosed by the U.S. patent.